Dante Alighieri: from Letter X: to Can Grande della Scala

(emphasis added -- GF)

For the clarification of what I am going to say, then, it should he understood that there is not just a single sense in this work: it might rather be called polysemous, that is, having several senses. For the first sense is that which is contained in the letter, while there is another which is contained in what is signified by the letter. The first is called literal, while the second is called allegorical. or moral or anagogical. And in order to make this manner of treatment clear, it can be applied to the following verses: "When Israel went out of Egypt, the house of Jacob from a barbarous people, Judea was made his sanctuary, Israel his dominion." [Psalm 93:1-2]

Now if we look at the letter alone what is signified to us is the departure of the sons of Israel from Egypt during the time of Moses; if at the allegory, what is signified to us is our redemption through Christ; if at the moral sense, what is signified to us is the conversion of the soul from the sorrow and misery of sin to the state of grace; if at the anagogical, what is signified to us is the departure of the sanctified soul from bondage to the corruption of this world into the freedom of eternal glory. And although these mystical senses are called by various names, they may all be called allegorical, since they are all different from the literal or historical. For allegory is derived from the Greek alleon which means in Latin alienus ("belonging to another") or diversus ("different").